Surgical resection techniques for carcinoma of the pancreas have been perfected. Their success, however, relies heavily on early diagnosis, which is not easily achieved because the current agent used for pancreatic imaging, 75Se-selenomethionine has several short-comings. Recent work has indicated that aromatic amino acids have much higher pancreas to liver concentration ratios than does selenomethionine. It therefore is proposed that selenium containing analogs of phenylalanine and tryptophan be synthesized. The prepared substances will be administered to rats to determine their pharmacokinetics, biologic distribution, toxicity, and ultimate fate. Selenium levels in the tissues will be determined by atomic absorption spectrophotometry. Compounds that show in vivo stability and promising pancreas to liver ratios will be labeled with 75Se and then reevaluated using the gamma well counter to determine tissue distribution. A series of compounds containing aliphatic seleno amino acid groups, and substituted benzene rings will also be synthesized and tested to determine which structural parameters of the aromatic amino acids determine pancreatic uptake.